Tool with end effector force limiter

ABSTRACT

The invention provides surgical or diagnostic tools and associated methods that offer improved user control for operating remotely within regions of the body. In some embodiments these tools include a proximally-located actuator for the operation of a distal end effector, as well as proximally-located actuators for articulational and rotational movements of the end effector. Control mechanisms and methods refine operator control of end effector actuation and of these articulational and rotational movements. A force limiter mechanism protects the end effector and manipulated objects from the harm of potentially excessive force applied by the operator. The tool may also include other features. A multi-state ratchet for end effector actuation provides enablement-disablement options with tactile feedback. An articulation lock allows the fixing and releasing of both neutral and articulated configurations of the tool and of consequent placement of the end effector. A rotation lock provides for enablement and disablement of rotatability of the end effector.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation patent application of U.S. patentapplication Ser. No. 11/787,599, filed Apr. 16, 2007, now U.S. Pat. No.8,409,244 and entitled “Tool With End Effector Force Limiter,” which isincorporated by reference herein, in its entirety. This application isrelated to the following concurrently filed U.S. patent applications:Ser. No. 11/787,543 entitled “Tool with articulation lock” of Hegeman,Danitz, and Alvord, Ser. No. 11/787,605 entitled “Tool with multi-stateratcheted end effector” of Hinman, Ser. No. 11/787,607 entitled “Toolwith rotation lock” of Hinman and Danitz, and Ser. No. 11/787,608entitled “Articulating tool with improved tension member system” ofHegeman, Danitz, Bertsch, and Alvord.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

FIELD OF THE INVENTION

This invention relates to tools with end effectors whose actuatorscontrol aspects of end effector operation.

BACKGROUND OF THE INVENTION

The popularity of minimally invasive surgery has been growing rapidlydue to its association with decreased complication rates andpost-surgical recovery times. The instruments employed are generallyhand-operable and typically include a handle, a shaft that may or maynot be rotatably attached to the handle, a rotation knob rigidly fixedto the proximal end of the shaft near the handle in instances where theshaft is rotatably attached to the handle, and a tool or end effectorattached to the distal end of the shaft. To manipulate the instruments,they are held at the handle and typically pivoted about a pivot pointdefined by the entry incision, i.e., the incision made in the abdominalwall for laparoscopic procedures. The end effector may also be rotatedabout the shaft axis, as for example, by rotating a rotation knob, ifpresent. In use, these instruments have limited control and range ofmotion and become physically taxing as the length of the procedureincreases.

Surgical procedures such as endoscopy and laparoscopy typically employinstruments that are steered within or towards a target organ or tissuefrom a position outside the body. Examples of endoscopic proceduresinclude sigmoidoscopy, colonoscopy, esophagogastroduodenoscopy, andbronchoscopy, as well as newer procedures in natural orificetransluminal endoscopic surgery (“NOTES”). Traditionally, the insertiontube of an endoscope is advanced by pushing it forward, and retracted bypulling it back. The tip of the tube may be directed by twisting andgeneral up/down and left/right movements. Oftentimes, this limited rangeof motion makes it difficult to negotiate acute angles (e.g., in therectosigmoid colon), creating patient discomfort and increasing the riskof trauma to surrounding tissues.

Laparoscopy involves the placement of trocar ports according toanatomical landmarks. The number of ports usually varies with theintended procedure and number of instruments required to obtainsatisfactory tissue mobilization and exposure of the operative field.Although there are many benefits of laparoscopic surgery, e.g., lesspostoperative pain, early mobilization, and decreased adhesionformation, it is often difficult to achieve optimal retraction of organsand maneuverability of conventional instruments through laparoscopicports. In some cases, these deficiencies may lead to increased operativetime or imprecise placement of components such as staples and sutures.

Recently, surgical instruments, including minimally invasive surgicalinstruments, have been developed that are more ergonomic and which havea wider range of motion and more precise control of movement. Theseinstruments may include mechanisms that articulate using a series oflinks coupled with one or more sets of tension bearing members, such ascable. As with conventional instruments used in minimally invasivesurgery, rotation of the shaft and end effector with respect to thehandle is an important feature of cable and link type instruments to aidwith dissecting, suturing, retracting, knot tying, etc. Ergonomic,flexible, and intuitive mechanisms that facilitate manual control of theend effectors of such instruments are also important factors as medicalprocedures become more advanced, and as surgeons become moresophisticated in their operating abilities. Further improvements in thefeatures and design of surgical instruments are desirable.

SUMMARY OF THE INVENTION

Some surgical or diagnostic instruments have an end effector whoseoperation is controlled by a movable end effector actuator. Inparticular, some instruments have operation states in which a forceapplied to the end effector actuator may be reflected in a forcedelivered by the end effector. It may at times be desirable to limit theforce delivered by the end effector, regardless of the amount of forceapplied to the end effector actuator. This invention provides methodsand devices for limiting the force delivered by an end effector.

Some embodiments of the invention comprise a surgical or diagnostic toolcomprising an end effector at a distal end of the tool and an endeffector actuator at a proximal end of the tool. The end effectoractuator is operatively connected to the end effector through a linkageto deliver an actuation force from the end effector actuator to the endeffector in response to movement of the end effector actuator. The toolfurther comprises a force limiter adapted to establish an upper limit onthe actuation force that may be delivered to the end effector by the endeffector actuator.

In some embodiments, the tool further comprises a handle supporting theend effector actuator, the end effector actuator being movable withrespect to the handle. The tool may comprise a stop element engagablewith the end effector actuator to stop its motion. In some embodiments,the force limiter is adapted to deform in response to actuation forcedelivered by the end effector actuator.

Some embodiments of the force limiter comprise a spring in the linkage.The spring may be pre-loaded to a pre-determined stress within thelinkage. The spring may be formed from a superelastic shape memorymaterial treated so as to bend when the upper limit of the actuationforce is applied to the end effector by the end effector actuator. Thesuperelastic shape memory material may have a plateau stress level, andthe spring may be disposed within the linkage so at to be pre-loaded atleast about to the plateau stress level. The tool may include both aspring and a stop element engagable with the end effector actuator tostop its motion.

In some embodiments, the end effector is operably connected to the endeffector actuator at least in part through the force limiter. The forcelimiter may be disposed between the end effector actuator and thelinkage. In some embodiments, the end effector actuator is operablyconnected to the linkage such that movement of the end effector actuatormoves the linkage. Movement of the end effector actuator with respect tothe linkage may vary when the upper limit of the actuation force isreached.

In some embodiments the force limiter comprises a tension bearing memberin the linkage. In some of these embodiments, the tension memberincludes a superelastic shape memory material that may be pre-stretchedto a predetermined stress when assembled into the linkage. In sometypical embodiments, the predetermined stress may correspondapproximately to the upper limit of the actuation force that is to beapplied to the end effector by the end effector actuator.

In some embodiments, the end effector comprises a movable force deliverysurface, and in some embodiments, the end effector may comprise a pairof jaws. In some embodiments, the tool comprises a shaft disposedbetween the end effector and the end effector actuator. The tool mayalso comprise an articulation mechanism for manipulating angularorientation of the end effector with respect to the shaft. Thearticulation mechanism in turn may comprise a proximal link and a distallink spaced apart from the proximal link. In such embodiments, movementof the proximal link causes corresponding relative movement of thedistal link and angular movement of the end effector with respect to theshaft.

Embodiments of the invention comprise a method of operating a surgicalor diagnostic tool, the tool as summarized above, where the method ofuse comprises placing the end effector at a target site, applying anactuation force to the end effector actuator, delivering at least someof the actuation force through the end effector to the target site, andlimiting the magnitude of the delivered actuation force to an upperlimit.

The step of applying an actuation force may comprise moving the endeffector actuator. In some embodiments, the tool used in the methodfurther comprises a handle supporting the end effector actuator, and thestep of moving the end effector actuator comprises moving the endeffector actuator with respect to the handle. The tool may comprise astop element, and the moving step may then comprise engaging the endeffector actuator with the stop element.

The method of using a surgical or diagnostic tool, as summarized above,may include the use of a tool that further comprises a force limiter,and the limiting step of the method may further comprise deforming theforce limiter. The force limiter may comprise a spring, and the limitingstep may then comprise deforming the spring. In some embodiments, thedeforming step comprises increasing strain of the spring withoutsubstantially increasing stress of the spring. In other embodiments, theforce limiter comprises a tension bearing member, and the limiting stepmay include tensioning the member. In some of these embodiments, thedeforming step may include the tension member stretching in response tothe tensioning. In some of these embodiments, the step of limiting themagnitude of the delivered actuation force includes the stretching ofthe tension member.

The step of delivering the force may comprise moving the end effector,and the limiting step may comprise ceasing movement of the end effectordespite continued movement of the end effector actuator. In someembodiments, the end effector comprises jaws, and the step of deliveringa force to the target site comprising moving the end effector jaws.

In some embodiments of the method of use, the tool further comprises ahandle supporting the end effector actuator and a shaft disposed betweenthe handle and the end effector, and the method further comprises movingthe handle angularly with respect to the shaft to move the end effectorangularly with respect to the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe claims that follow. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings which are briefly described below.

FIG. 1 is a front perspective view of an articulatable surgical tool.

FIG. 2 is perspective view of a surgical tool in an articulatedposition.

FIG. 3 is an exposed side view of a surgical tool with an end effectoractuator and an end effector both in an open position.

FIG. 4 is an exposed side view of a surgical tool with an end effectoractuator and an end effector both in a closed position.

FIG. 5 is a side view of the proximal portion of a tool, showing thehandle and proximal end of the shaft, with an articulation lockingsleeve in a distal and unlocked position.

FIG. 6 is a side view of the proximal portion of a tool, showing thehandle and proximal end of the shaft, with an articulation lockingsleeve in a proximal and locked position.

FIG. 7 is an exposed view of a portion of a tool from an overhead distallooking perspective, the portion including the handle, locking rotationknob, and a proximal link.

FIG. 8 is a cutaway view of a portion of the handle, knob, and aproximal link.

FIG. 9 is an exposed view of a handle from a distal-looking perspective.

FIG. 10 is an exposed view of a handle from a proximal-lookingperspective.

FIG. 11 is an exposed side view of a surgical tool with an end effectoractuator and an end effector both in an open position, the end effectorjaws embracing an object.

FIG. 12 is an exposed side view of a surgical tool with an end effectoractuator in a closed position and the end effector in an open position,the end effect or jaws embracing an object, the force applied by theclosed end effector actuator having been absorbed by a force limiter.

FIG. 13 is a cross sectional view of the force limiter locale within thehandle of a tool, showing the end effector actuator, force limiter, androd actuator, the end effector actuator in an open position, the forcelimiter minimally bent at preload tension.

FIG. 14 is a cross sectional view of the force limiter locale within thehandle as in FIG. 13, except the end effector actuator is in a closedposition, the force limiter is fully bent, absorbing force from theclosed end effector actuator.

FIG. 15 is a side perspective, slightly distal-looking view of arotatable rod actuator, a ledge that engages the force limiter at thebottom.

FIG. 16 is a side perspective, more sharply distal-looking view of arotatable rod actuator, a ledge that engages the force limiter at thebottom.

FIG. 17 is a cross sectional view of the force limiter locale of aninstrument showing the end effector actuator in an open position, andthe force limiter having a minimal bend.

FIG. 18 is a cross sectional view of the force limiter locale of aninstrument with the showing the end effector actuator in an closedposition, and the force limiter having absorbed force from the closureof the end effector actuator, and thereby bent.

FIG. 19 is a view of the force limiter locale of an instrument, similarto the view provided in FIGS. 17 and 18, but with a different embodimentof a force limiter spring.

FIG. 20 is a cross sectional side view of a force limiter locale in atool, wherein the force limiter is embodied as a linear actuator for anend effector actuating rod.

DETAILED DESCRIPTION OF THE INVENTION

The invention described herein relates to a force limiter mechanismintervening between force applied by a user at the proximal end of atool and the transmission of that force to the distal end of a tool.Embodiments of the invention may be applied to non-articulatinginstruments, but many typical embodiments are applied to the operationof articulating tools. Steerable articulating instruments are describedin U.S. Pat. No. 7,090,637; US 2005/0107667; US 2005/0273084; US2005/0273085; and US 2006/0111210. The articulating mechanisms of thetools described in those publications use multiple pairs of segments orlinks controlled, e.g., by multiple sets of cables. Depending upon thespecific design of the device, the links can be discrete segments (asdescribed, e.g., in U.S. Pat. No. 7,090,637) or discrete portions of aflexible segment (as described, e.g., in US 2005/0173085). Theinstrument may also include steerable or controllable links of varioustypes, e.g., as described in US 2005/0273084, US 2006/0111209, and US2006/0111210. Some articulating or steerable instruments have anarticulating capability provided by minimal numbers of link pairs andcables connecting such links, U.S. Pat. No. 5,916,146 of Alotta, forexample, has a mechanism comprising a single pair of links controlled bya single cable.

When using such articulating instruments, a user may manipulate theproximal end of the instrument, thereby moving one or more proximallinks of the articulation mechanism. This movement results in relativemovement of the distal link(s) corresponding to the proximal link(s). Itmay at times be desirable to lock or otherwise maintain the straight orbent shape of the instrument. In certain embodiments of this invention,the shape of the instrument is maintained by preventing movement of atleast one of the proximal links with respect to the rest of theinstrument. In other embodiments, a friction-based articulation lockingmechanism locks all links, proximal and distal; these embodiments aredisclosed in the concurrently filed and hereby incorporated application“Tool with articulation lock” of Hegeman, Danitz, Hinman, and Alvord.

Many articulating instruments have end effectors controlled by movableactuators; a movable end effector actuator maybe, for example, amoveable portion of the handle of an instrument, or a thumbpiece. Insome embodiments, the end effector actuator has an operation state inwhich movement is permitted in only one direction and an operation statein which the actuator is free to move in two or more directions. Certainembodiments of this invention provide methods and devices for changingthe operational state of an end effector actuator between a state inwhich movement of the actuator is permitted in only one direction; astate in which the actuator is permitted to move in two directions inresponse to continuous user input to a state changer, and a state inwhich the actuator is permitted to in two directions in the absence ofuser input to a state changer.

FIGS. 1-20 show embodiments or portions of an articulatable tool 100with an end effector 102 at its distal end and an end effector actuator104 within a handle 106 at its proximal end. Instrument 100 may be used,e.g., in a laparoscopic procedure requiring grasping or cutting within apatient. Proximal articulation links 108 and 110 extend distally fromhandle 106, and distal articulation links 112 and 114 extend proximallyfrom end effector 102. Proximal link 108 is connected to and moves withhandle 106. Likewise, distal link 112 is connected to and moves with endeffector 102. A bushing 115 separates links 110 and 112. Bushing 115 hasconvex surfaces at its proximal and distal ends that engage withcorresponding concave surfaces on links 108 and 110. Further details ofball and socket links suitable for use with this invention may be foundin US 2005/0273084, US 2006/0111209, and US 2006/0111210. An elongatedshaft 116 is disposed between the proximal links and the distal linksEmbodiments of the shaft may either be rigid or flexible, althoughembodiments shown herein are depicted as being rigid.

As seen in FIGS. 3 and 4, a set of control cables 118 is attached toproximal link 108, extends through proximal link 110, shaft 116 anddistal link 114, and is attached to distal link 112. A second set ofcontrol cables 120 is attached to proximal link 110, extends throughshaft 116 and is attached to distal link 114. In this embodiment, thereare three control cables 118 in the first set and three control cables120 in the second set. It should be appreciated, however, that othernumbers of control cables may be used to connect corresponding proximaland distal links. In addition, mechanisms other than cables may be usedto connect corresponding links.

As shown in FIG. 2, movement of handle 106 and proximal link 108 withrespect to proximal link 110 moves end effector 102 and distal link 112in a relative and corresponding manner. Likewise, movement of proximallink 110 with respect to shaft 116 moves distal link 114 with respect toshaft 116 in a relative and corresponding manner, also as shown in FIG.2. This relative articulation movement provides a way for a user toremotely manipulate the end effector through movement of the handle. Therelative movement of the distal link that corresponds to the proximallink movement may either mirror the movement of the proximal link or bereciprocal to it, depending on whether the cables are strung directly(for reciprocal movement), or whether they are rotated 180 degrees (formirrored movement) between the proximal and distal links.

In order to maintain a particular position of the end effector withrespect to the shaft, the articulating tool of this invention may havean articulation lock. In the embodiment shown in FIGS. 1-6, thearticulation lock includes a movable rigid sleeve 130. In the unlockedposition shown in FIGS. 1-5, sleeve 130 is distal to proximal links 108and 110. In the locked position shown in FIG. 6, however, sleeve 130 hasbeen moved proximally to a position adjacent to and covering links 108and 110 as well as the proximal end of shaft 116, thereby blockingrelative movement between links 108 and 110 and between link 110 andshaft 116. In this locked position, relative movement between distallinks 112 and 114 and between link 114 and shaft 116 is prevented aswell.

As shown in FIG. 6, a sleeve support mechanism 132 extends proximallyfrom shaft 116 to provide sliding support for sleeve 130. A distal stop134 provides a limit of distal movement of sleeve 130; a similar stop(not shown) is provided on or within handle 106 to limit proximalmovement of sleeve 130. Detents, ridges or other mechanisms may beprovided to maintain the sleeve in its proximal or distal positions andto provide tactile feedback to the user regarding the position of thesleeve. Further detail on mechanisms that control permissibility ofarticulation in articulatable instruments is provided in theconcurrently filed and hereby incorporated U.S. Patent Applicationentitled “Tool with articulation lock” of Hegeman, Danitz, Hinman, andAlvord.

The description now turns briefly to features of tools that includeembodiments of an inventive force limiter, such features includingrotatability of the distal end effector by proximal mechanisms, andmechanisms by which rotatability is allowed or disallowed by a lockingmechanism. Provided here will be a brief description of some theseembodiments; a full disclosure of such embodiments is provided inconcurrently filed and hereby incorporated U.S. Patent Applicationentitled “Tool with rotation lock” by Hinman and Danitz.

The end effector 102 of tool 100 may be rotated with respect to handle106 and then locked so that further rotation between end effector 102and handle 106 is prevented. A rotation knob 101 is disposed at leastpartially around link 108. In the locked position, teeth 103 formed onthe proximal face of knob 101 engage corresponding teeth 105 formed on adistal face of handle 106, as seen in FIG. 10. Handle 106 may be made intwo pieces; two views of one of the two pieces are shown in FIGS. 9 and10.) In this embodiment, the rotation lock is self-locking due to theaction of a spring 107 biasing knob 101 proximally into engagement withhandle 106, as shown in FIG. 8.

When moved distally against the bias of spring 107, the teeth 103 ofknob 101 disengage from the teeth 105 of handle 106. This disengagementpermits knob 101, links 108 and 110, shaft 106, links 112 and 114, andend effector 102 to rotate with respect to handle 106. This actionpermits the end effector to be rotated in any articulated configuration.When the end effector has been rotated the desired amount, release ofknob 101 permits the two sets of teeth to re-engage, thereby locking thedevice against further rotation. In one embodiment, knob 101 is made intwo pieces, an inner member 109 and an outer member 111, as shown inFIG. 8. The teeth 103 are formed on the inner member 109. Indentationsor knurls 113 (FIG. 7) may be formed on knob 101 to facilitate grasping.

Description now turns to consideration of a force limiter thatintervenes in the transmission of force from a user to an end effectoron a tool. In the embodiments illustrated in FIGS. 1-20, the endeffector 102 is a pair of jaws. Other end effectors (surgical,diagnostic, non-medical mechanical manipulators, etc) and end effectoractuators may be used with the articulating tool of this invention.Actuation force is transmitted from movable end effector actuator 104through a transmission or linkage that includes a rotatable rod actuator122, a movable rod terminator 124, and a tension bearing member, such asrod 125 connected to rod terminator 124, as shown in FIGS. 3, 4, 7, and8. Rod 125 passes through link 108, bushing 115, link 110; the shaft(not shown in FIG. 8) and the distal links (not shown in FIG. 8) toreach and actuate the end effector. Rod terminator 124 encases a portionof rod 125 within handle 106 to prevent the rod 125 from buckling undera compressive load. Similar features may be provided throughout the tool100 to laterally constrain rod 125. (See further detail in concurrentlyfiled patent application “Articulating tool with improved tension membersystem” of Hegeman, Danitz, Bertsch, and Alvord). End effector actuator104 and rod actuator 122 are both rotatably mounted on a common bushing202 so as to be able to be rotated with respect to each other to moverod 125 and thereby actuate end effector 102.

A force limiter such as a leaf spring 200 attached to end effectoractuator 104 extends to a ledge 204 (shown best in FIGS. 15 and 16)formed in rod actuator 122 and provides for force transmission from theend effector actuator 104 to rod actuator 122 as actuator 104 is movedtoward handle grip 206. Actuator 104 may be moved until a stop element208 on a surface of actuator 104 engages a stop element 210 on grip 206,as shown in FIGS. 3 and 4 and in FIGS. 11 and 12. In FIG. 4, the endeffector jaws are closed when actuator 104 engages stop element 210. InFIG. 12, on the other hand, the jaws have encountered an object 212. Theforce limiter of this invention permits the actuator 104 to continuemoving toward stop element 210 even if the jaws have stopped closingwhile limiting the amount of force applied by the end effector on theobject, as explained below.

Spring or force limiter 200 rotationally biases the rod actuator 122against the end effector actuator 104 such that surface 250 of rodactuator 122 contacts surface 252 of end effector actuator 104 as shownin FIG. 13. In this embodiment, force limiter 200 is formed from a shapememory material (such as Nitinol) that is in its superelastic state.Force limiter 200 is pre-biased (to, e.g., 1.5% strain) so that it is ata known state along its stress/strain curve. This pre-loading of spring200 ensures that, until a predetermined threshold force is reached (asdescribed below), end effector 104, spring 200, bushing 202, and rodactuator 122 all move together and act as a rigid body. If the jaws ofend effector 102 encounter an obstacle (as shown in FIG. 12) and theforce applied through actuator 104 exceeds the threshold force, thestress on force limiter 200 reaches the characteristic plateau of thestress/strain curve, and force limiter 200 bends elasticallysubstantially without delivering any further rotational movement to rodactuator 122, as shown in FIG. 14.

In one embodiment, the instrument has a force limiter 200 thatestablishes an upper limit on the actuation force that may be deliveredto the end effector by the end effector actuator. In one embodiment,spring 200 may be formed from an elastomeric or spring metal material.In other embodiments, the material used to form spring 200 is selectedand/or treated to provide a stress-strain relationship with acharacteristic plateau region in which stress does not substantiallychange over a range of strain values. For example, in the instrumentshown in FIGS. 1-19, spring 200 is formed from a superelastic shapememory material, such as Nitinol. The Nitinol is selected and treated sothat spring 200 is in the Austenitic phase at the temperatures at whichthe instrument will be used. The material properties when so treatedprovide for substantially no change in stress over a range of strainvalues, e.g., 1.5% to 6% strain.

When assembling the instrument, spring 200 may be pre-loaded so that itsstrain is at or near the beginning of the stress plateau. In the absenceof any counterforce resisting closing of the jaws of end effector 102,movement of end effector actuator 104 toward handle grip 206 transmitsan actuation force through spring 200 to rod actuator 122, rodterminator 124, rod 125, and finally to end effector 102. As shown inFIGS. 11 and 12, if the jaws of end effector 102 encounter an object212, actuator 104 will experience a counterforce as it continues itsmovement toward grip 206. When the counterforce exceeds thecharacteristic plateau stress of spring 200, spring 200 will deformwithout substantially increasing the strain of spring 200, therebymaintaining the actuation force transmitted through spring 200 and theremaining components of the actuation linkage. In the illustratedembodiment, the material comprising spring 200 may be selected and/ortreated so that the spring remains in the stress plateau throughout itsrange of motion up to and including the point at which end effectoractuator meets the limit stop 210 on grip 206.

Description now turns briefly to an actuator movement controller thatmay be included in embodiments of the invention depicted in FIGS. 1-20.Embodiments may include a shaft having a proximal end and a distal end,an end effector at the distal end of the shaft, a movable end effectoractuator at the proximal end of the shaft and operably connected to theend effector, and an actuator movement controller operably connectableto the end effector actuator. The actuator movement controller includesa user-activated state changer that is changeable among several states.These states include ones in which the movement controller is (1)enabled and engaged with the end effector actuator to prevent movementof the end effector actuator in at least one of two opposing directions,(2) enabled and disengaged from the end effector actuator to permitmovement of the end effector actuator in a first direction and a seconddirection opposite to the first direction in response to continuous userinput via the state changer, and (3) disabled to permit movement of theend effector actuator in a first direction and a second directionopposite to the first direction in the absence of user input via thestate changer. In some embodiments, the first state (enabled andengaged) may prevent movement of the end effector actuator in bothdirections.

In some embodiments the end effector includes jaws. In some embodimentsthe actuator movement controller includes a ratchet. In some embodimentsthe state changer includes a movable trigger. In some embodiments with atrigger, the state changer further includes a toggle operativelyconnected to the trigger so as to be movable with the trigger and to berotatable with respect to the trigger. In some of the embodiments with atoggle, the toggle is operatively connected to the trigger so as to movewith the trigger without rotating with respect to the trigger when themovement controller is enabled. Embodiments of the multi-state ratchetmechanism that controls the end effector and the end effector actuatorare disclosed in detail in the U.S. Patent Application entitled andhereby incorporated “Tool with multi-state ratcheted end effector” byHinman.

The embodiments described herein, by way of example, provide an actuatormotion controller using a ratchet mechanism that, when engaged, permitsthe end effector actuator to be moved in one direction (to, e.g., closea pair of jaws) while preventing the end effector actuator to move inthe other direction (to, e.g., maintain the jaws in their closed state).In FIG. 3, for example, the ratchet is formed from a rack of teeth 220extending from end effector actuator 104. A movable pawl 222 isrotatably mounted within handle 106. A user may change the operationstate of the ratchet by operating a trigger 224 which connects to pawl222 through a toggle 226.

Returning now to the force limiter, FIGS. 17 and 18 show alternativeembodiments of a force limiter according to this invention. Elementscommon to the embodiment shown in FIGS. 1-20 have been given the samereference numbers. As before, end effector actuator 104 and a rodactuator 502 independently rotate about a common bushing 202. Thisembodiment replaces the spring of the embodiment shown in correspondingFIGS. 3 and 4 with a spring 500 attached to rod actuator 502. Spring 500engages end effector actuator at an engagement surface 504. As in theembodiment shown in FIGS. 1-16, spring 500 may be made from asuperelastic shape memory material, such as Nitinol, and may beconfigured by design and/or assembly protocol such that it is pre-loadedto be at or near the plateau in its stress/strain curve. In that way, ifa threshold actuation force is met, spring 500 deforms to the shapeshown, e.g., in FIG. 18 without any additional stress being transmittedthrough the device's linkage to the end effector.

FIG. 19 shows yet another alternative embodiment of a force limiteraccording to the invention in a view that is similar to those of FIGS.17 and 18. As before, an end effector actuator 104 a and a rod actuator602 independently rotate about a common bushing 202. In this embodiment,a coil spring 600 comprising a superelastic shape memory material suchas Nitinol is pre-loaded and disposed between end effector actuator 104a and rod actuator 602. Pre-loading stress into the spring can place itat or near the plateau in its stress/strain curve, as described above.Consequently, as a threshold actuation force is applied, spring 602deforms it without transmitting any additional stress through thedevice's linkage to the end effector.

FIG. 20 shows still another embodiment of a force limiter. In thisembodiment, the proximal end of end effector actuation rod 125(optionally formed from Nitinol) is held in rod terminator 705. Thedistal end of a force limiter 700 is also held in rod terminator 705,while the proximal end of force limiter 700 is held in a force limiterhousing 710. Rod terminator 705 fits into a distal opening of forcelimiter housing 710, but the two parts can be separated, as describedbelow. In this embodiment, force limiter 700 is preloaded with apredetermined amount of stress at about or just below the plateau stressof a super elastic material, by, e.g., providing 1.5% strain in theposition shown in FIG. 20. The distal portion of force limiter housing710 is attached to a movable slide member 715, which fits in a fork 720extending from end effector actuator 704. When end effector actuator 704is rotated with a subthreshold force about bushing 702, fork 720 movesslide 715, force limiter housing 710, rod terminator 705 and rod 125proximally to actuate the end effector. If the force applied to endeffector actuator 704 exceeds the threshold force (due, e.g., to anobject held in end effector jaws), force limiter 700 will stretch,separating force limiter housing 710 from rod terminator 705, so thatfurther movement of end effector actuator 704 will not cause any furthermovement of rod 125. This feature limits the force delivered by the endeffector actuator to the end effector, and consequently the forceexerted by the end effector, to the threshold force.

In yet another embodiment (not shown) similar to that of FIG. 20, therod 125 extends back into the linearly movable force limiter housing710. By using Nitinol for rod 125, or another suitable super elasticmaterial, if the force applied to rod 125 by end effector actuator 704induces a stress equal to the plateau stress of rod 125, then rod 125will stretch without increasing the force applied to the end effector.

While the inventive surgical instruments and devices have been describedin some detail by way of illustration, such illustration is for purposesof clarity of understanding only. It will be readily apparent to thoseof ordinary skill in the art in light of the teachings herein thatcertain changes and modifications may be made thereto without departingfrom the spirit and scope of the appended claims For example, while theforce limiter mechanism described herein typically has been in thecontext of a tool with an articulating mechanism comprising at least twolinks, the rotation knobs may be used in an instrument comprising only asingle link, a multiplicity of links, with any number of cables or cablesets operably connecting the links, or, alternatively, embodiments ofthe inventive force limiter may be used with surgical instruments thatdo not articulate at all. Further, while the shaft of depictedinstruments including embodiments of the force effector have beendepicted as rigid, in some variations it may be desirable to have thehandle affixed to a shaft that is flexible. Still further, while theinventive force limiter has been described in the context of a toolcomprising a multi-state ratchet mechanism, some embodiments of theforce limiter include tools without a ratchet mechanism. Lastly, whilethe context of the invention is typically understood to be surgical ormedical diagnostic procedures, embodiments of the force limiter or toolshaving such a mechanism may have utility in other, non-medical contextsas well.

What is claimed is:
 1. A medical tool comprising: an end effector at adistal end of the tool; an end effector actuator at a proximal end ofthe tool, the end effector actuator being operatively connected to theend effector through a linkage to deliver an actuation force from theend effector actuator to the end effector in response to movement of theend effector actuator, the linkage comprising an elongated actuationcomponent defining an actuation axis; a rod terminator coupled to theelongated actuation component; and a force limitation assembly adaptedto establish an upper limit on the actuation force delivered to the endeffector by the end effector actuator, the force limitation assemblyincluding an elongated force limiter component extending within andcoupled to a force limiter housing, the force limitation assemblymovably coupled to the end effector actuator and the force limiterhousing removably coupled to the rod terminator, wherein when theactuation force delivered to the end effector actuator does not exceedthe upper limit, the actuation force delivered to the end effectoractuator causes linear movement of the elongated actuation component andthe force limitation assembly along the actuation axis and wherein whenthe actuation force delivered to the end effector actuator exceeds theupper limit, the linear movement of the elongated actuation component isterminated.
 2. The medical tool of claim 1 wherein when the actuationforce exceeds the upper limit, movement of the end effector actuatorcauses at least a portion of the elongated actuation component tostretch.
 3. The medical tool of claim 2 wherein the at least a portionof the elongated actuation component is formed from a shape memorymaterial.
 4. The medical tool of claim 1 wherein a portion of theelongated actuation component is held within the force limiter housingwhen the actuation force does not exceed the upper limit and separatesfrom the force limiter housing when the actuation force exceeds theupper limit.
 5. A medical tool comprising: an end effector at a distalend of the tool; an end effector actuator at a proximal end of the tool,the end effector actuator being operatively connected to the endeffector through a linkage to deliver an actuation force from the endeffector actuator to the end effector in response to movement of the endeffector actuator, the linkage comprising an elongated actuationcomponent defining an actuation axis; and a force limitation assemblyadapted to establish an upper limit on the actuation force delivered tothe end effector by the end effector actuator, the force limitationassembly movably coupled to the end effector actuator and removablycoupled to the elongated actuation component, wherein when the actuationforce delivered to the end effector actuator does not exceed the upperlimit, the actuation force delivered to the end effector actuator causeslinear movement of the elongated actuation component and the forcelimitation assembly along the actuation axis and wherein when theactuation force delivered to the end effector actuator exceeds the upperlimit, the linear movement of the elongated actuation component isterminated, wherein the force limitation assembly includes an elongatedforce limiter component extending within a force limiter housing, andwherein the elongated actuation component comprises a rod terminatorincluding a channel sized to receive a distal end of the force limitercomponent and including a coupling portion sized to extend within theforce limiter housing.
 6. The medical tool of claim 5 wherein when theactuation force delivered to the end effector actuator exceeds the upperlimit, the coupling portion of the rod terminator separates from theforce limiter housing.
 7. The medical tool of claim 5 wherein the forcelimiter component is coupled to the rod terminator pre-loaded with apredetermined stress.
 8. The medical tool of claim 1 wherein when theactuation force does not exceed the upper limit, the actuation forcedelivered to the end effector actuator causes sliding movement of theforce limitation assembly along the actuation axis.
 9. The medical toolof claim 1 wherein the actuation force on the end effector actuatorcauses rotational movement of the end effector actuator about a pivot.10. The medical tool of claim 1 further comprising a movable slidemember coupled to the force limitation assembly and slidable linearlyalong the actuation axis, wherein the end effector actuator includes aforked component that pivots with respect to the movable slide memberwhen the actuation force is delivered to the end effector actuator. 11.The medical tool of claim 1 wherein the end effector comprises a pair ofjaws.
 12. The medical tool of claim 1, wherein the rod terminatorincludes a channel sized to receive a distal end of the force limitercomponent and includes a coupling portion sized to extend within theforce limiter housing.
 13. The medical tool of claim 12, wherein whenthe actuation force delivered to the end effector actuator exceeds theupper limit, the coupling portion of the rod terminator separates fromthe force limiter housing.
 14. The medical tool of claim 1, wherein theforce limiter component is coupled to the rod terminator pre-loaded witha predetermined stress.
 15. The medical tool of claim 5, wherein whenthe actuation force does not exceed the upper limit, the actuation forcedelivered to the end effector actuator causes sliding movement of theforce limitation assembly along the actuation axis.
 16. The medical toolof claim 5, wherein the actuation force on the end effector actuatorcauses rotational movement of the end effector actuator about a pivot.17. The medical tool of claim 5, further comprising a movable slidemember coupled to the force limitation assembly and slidable linearlyalong the actuation axis, wherein the end effector actuator includes aforked component that pivots with respect to the movable slide memberwhen the actuation force is delivered to the end effector actuator. 18.The medical tool of claim 5 wherein the end effector comprises a pair ofjaws.
 19. A medical tool comprising: an end effector at a distal end ofthe tool; an end effector actuator at a proximal end of the tool, theend effector actuator being operatively connected to the end effectorthrough a linkage to deliver an actuation force from the end effectoractuator to the end effector in response to movement of the end effectoractuator, the linkage comprising an elongated actuation componentdefining an actuation axis; a force limitation assembly adapted toestablish an upper limit on the actuation force delivered to the endeffector by the end effector actuator, the force limitation assemblyincluding an elongated force limiter component extending within andcoupled to a force limiter housing, the force limitation assemblymovably coupled to the end effector actuator and removably coupled tothe rod terminator; and a rod terminator coupled to the elongatedactuation component and including a channel sized to receive a distalend of the force limiter component, the rod terminator removably coupledto the force limiter housing, wherein when the actuation force deliveredto the end effector actuator does not exceed the upper limit, theactuation force delivered to the end effector actuator causes linearmovement of the elongated actuation component and the force limitationassembly along the actuation axis and wherein when the actuation forcedelivered to the end effector actuator exceeds the upper limit, thelinear movement of the elongated actuation component is terminated. 20.The medical tool of claim 19, wherein when the actuation force deliveredto the end effector actuator exceeds the upper limit, the rod terminatorseparates from the force limiter housing.
 21. The medical tool of claim19, wherein the force limiter component is coupled to the rod terminatorpre-loaded with a predetermined stress.
 22. The medical tool of claim19, wherein when the actuation force does not exceed the upper limit,the actuation force delivered to the end effector actuator causessliding movement of the force limitation assembly along the actuationaxis.
 23. The medical tool of claim 19, wherein the actuation force onthe end effector actuator causes rotational movement of the end effectoractuator about a pivot.
 24. The medical tool of claim 19, furthercomprising a movable slide member coupled to the force limitationassembly and slidable linearly along the actuation axis, wherein the endeffector actuator includes a forked component that pivots with respectto the movable slide member when the actuation force is delivered to theend effector actuator.
 25. The medical tool of claim 19, wherein the endeffector comprises a pair of jaws.